Tauopathies are a class of neurodegenerative disorders characterized by abnormal aggregation of the tau protein that affect over 5 million people in the United States and include diseases such as Progressive supranuclear palsy (PSP), Corticobasal degeneration (CBD), and some forms of Frontotemporal Dementia (FTD). Tauopathy is also a prominent feature of Alzheimer's disease. In addition to neurodegeneration, tauopathies are associated with increased sleep disturbances including insomnia, excessive daytime sleepiness, and rapid eye movement (REM) sleep behavior disorder. Up to 76% of FTD patients exhibit sleep disturbances of some kind and a high percentage of CBD and PSP patients suffer from insomnia. These sleep disorders are a major cause of institutionalization. Sleep is an important biological function that facilitates learning and memory as well as metabolic homeostasis of proteins within the brain. Despite the importance of sleep and the high prevalence of sleep disturbances in tauopathies, little is known about the role of tau pathology in sleep disruption. The objective of this work is to study the interaction between sleep disturbances and tau pathology, which could ultimately lead to better treatments for tauopathy-related sleep disorders, improvements in care, and decreases in institutionalization, as well as possibly providing a strategy for slowing disease progression itself. Preliminary analysis of sleep/wake behavior in aged tauopathy mouse models of FTD with Parkinsonism-17 (P301S) demonstrates that tau pathology significantly decreases delta power during non-rapid eye movement sleep (NREM) sleep and theta power during REM sleep compared to wild-type controls. Aged P301S human tau mice also show a trend towards increased time in wake and decreased time in sleep. We hypothesize that sleep disturbances increase with tau pathology progression and that sleep deprivation results in increased tau pathology in the brain. This proposal uses in vivo quantitative electroencephalography with electromyography to analyze the effect of tau pathology progression on sleep/wake behavior as well as anti-tau antibody treatment to determine if insoluble tau is causative of sleep deficits. Additionally, this project ill investigate the effects of chronic and short-term sleep deprivation on tau pathology as well as tau levels in the brain interstitial fluid to determine if decreased sleep, as seen in tauopathy patients, affects disease progression.